Earth digging apparatus



Aug. 30, 1960 H. v. OLDS EARTH DIGGING APPARATUS 5 Sheets-Sheet 1 Filed Aug. 21, 1956 INVENTOR. HOWARD V. OLDS gg/Wm ATTORNEYS 5 Sheets-Sheet 2 ATTORNEYS Aug. 30, 1960 H. v. OLDS EARTH DIGGING APPARATUS Filed Aug. 21, 1956 PEG. 4

Aug. 30, 1930 Filed Aug. 21, 1956 H. v. OLDS 2,950,902

EARTH DIGGINC- APPARATUS 5 Sheets-Sheet 3 INVENTOR. HOWARD v. OLDS ATTORNEYS Aug. 30, 1960 H. v. OLDS 2,950,902

EARTH DIGGING APPARATUS Filed Aug. 21, 1956 5 Sheets- Sheet 4 FIG. 6

7 FIG. 8

INVENTOR. HOWARD V. OLDS ATTORNEYS Aug. 30, 1960 H. v. OLDS EARTH DIGGING APPARATUS Filed Aug. 21, 1956 5 Sheets-Sheet 5 FIG. 9

I711 3' QH 73a Efi' 2 4 I9 I9 11W 'EN TOR.

HOWARD V. OLDS 1 B fmi W1 u ATTORNEY? United States Patent EARTH DIGGING APPARATUS Howard V. Olds, 5923 Dixie Highway, Saginaw, Mich.

Filed Aug. 21, 1956, Ser. No. 605,293

17 Claims. (Cl. 25521) This invention relates to earth digging apparatus and more particularly to apparatus for digging a quadrilateral, preferably square, hole.

Machines of the kind with which the invention is concerned are particularly suitable for the excavating of graves, the digging of holes for septic tanks, utility poles and the like, and in other instances where it is desiped that the holes have straight sides and bottoms and where it is preferable that the hole be substantially no larger than the object to be placed therein.

So-called square hole diggers are known in the art, but those of which I have knowledge are not entirely satisfactory inasmuch as none of them has the boring angers so arranged as to occupy substantially the entire area which is to be excavated. Thus, between each anger will be a shell or ridge of earth which will adversely affect excavation operations. It is not possible for a plurality of angers to be so arranged as wholly to ocapy the area to be excavated, but one of the objects of this invention is to provide digging apparatus of the class referred to in which the arrangement of angers and the addition of other cooperating parts reduces the unoccupied area to such an extent that the adverse effects of the unoccupied area are negligible.

Another object of the invention is to provide earth digging apparatus which is capable of digging a hole having substantially straight side and bottom walls.

Another object of the invention is to provide digging apparatus having a plurality of earth boring angers grouped to dig a substantially square hole and including rotary disc cutters for cutting at the edges of the hole to assist the angers in boring into the earth.

A further object of the invention is to provide earth digging apparatus having a plurality of angers and cutting discs so arranged that the digging implements complement one another.

A further object of the invention is to provide power driven earth digging apparatus of the kind employing angers operable at such speed that loose earth will re main on the flights of the angers and which includes mechanism for effecting self-discharge of the loose earth from the angers.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description of a preferred form of the'invention when considered in conjunction with the appended claims and the accompanying drawings, in which:

Fi ure 1 is a fragmentary, side elevational View, with certain parts broken away, of earth digging apparatus constructed in accordance with the invention;

Figure 2 is a sectional view taken on the line 22 of Figure 1 and showing the arrangement of the angers;

Figure 3 is a sectional view taken on the line 3-3 of Figure 2 and showing one of the rotary disc or side cutters which cooperate with the angers to dig a hole having straight walls.

Figure 4 is a fragmentary, side elevational view of the angers with the skirt forming side panels removed;

ice

Figure 5 is an enlarged, fragmentary, rear elevational View showing a portion of the drive transmitting mech anism for driving the angers and side cutters;

Figure 6 is a fragmentary, top plan View of the ap-' paratus showing the driving motor and a portion of the drive transmitting mechanism;

Figure 7 is a fragmentary detail, partly in section and partly in plan of a portion of the drive transmitting mechanism arranged to drive the angers in earth boring direction;

Figure 8 is a view similar to Figure 7, but showing the transmission parts arranged to drive the angers in reverse direction;

Figure 9 is a fragmentary plan View of a part of the drive transmitting mechanism, other parts of which are omitted; and

Figure 10 is a view similar to Figure 9, but showing other parts of the drive transmission means.

Earth digging apparatus constructed in accordance with the invention comprises a main frame 1 including a platform 1a above which is a number of frame members 2a, which provide means to support parts of the apparatus located there and to provide means for enabling covering plates 2b to he secured in enclosing position. Below the platform 1a is a plurality of reinforcing channel or angle members 2, arranged to form a quadrangle or square, the ends of the members 2 being suitably secured as by welding or the like to journal bearings 3. Each of the journal bearings 3 also is secured to and extends through the platform 1a and mounts a rotatable shaft 4, conventional means (not shown) cooperating with the shafts to prevent vertical movement of the shaft relative to the bearing. Each of the shafts 4 has secured to the major portion of its depending length a helical flight 5 and each shaft 4 has a tapered or reduced lower end 6 provided with a helical flange or screw thread '7. Hereinafter, the assembly of a shaft 4, its flight 5, its tapered end 6 and the screw thread '7 will be referred to as a corner auger 8, or simply as an anger.

As is best shown in Figure 2, a number of frame elements 9 extends from the bearing members 3 of the corner angers 8 towards the center of the square defined by the frame members, and the end of each element 9 is welded or otherwise suitably fixed to a journal bearing 10 which extends through and is secured to the platform 1a. In the bearing 10 is rotatably journaled the shaft 11 of a main or central auger 12, the major portion of the shaft depending below the frame 1 and having one or more helical flights 13 fixed thereon. As is most clearly shown in Figure 4, the pitch of the flights 13 of the central anger is different from the pitch of the corner angers flights, the purpose of which will be explained hereinafter. The lower end 14 of the auger. shaft 12 is tapered or reduced in a manner similar to the corner angers shafts 4 and is similarly equipped with screw threads 15. As is shown in Figure 2, the arrangement of the angers 8 and 12 is quincuncial and the relative diameters or sizes of the angers are such that each of the corner angers 8 is substantially tangential to the central auger, there being only a small clearance between the flights of the central and the corner angers, respectively. This clearance effectively may be reduced or de-emphasized by the provision, on the lower end of each of the flights 13, of a rake tooth or projection 16 which extends radially outwardly and downwardly so as to be capable of passing under the lowermost edges of the corner auger flights 5 for a purpose yet to be explained.

At each corner of the main frame or platform 1 is welded 'or otherwise secured a bracket or similar part 17 (Figure 1) to provide mounts for a set of four plates 18 which depend below the platform 1a and form a quadrilateral, preferably square, enclosure for the angers. To

the inner surface of each of the plates 18 is bolted or welded a pair of generally channel shaped housing members 19 which are spaced from each other laterally of their respective supporting plates 18. The lower edges of the plates 18 are cut away or scalloped as at 20 (see Figure l), the channel members 19 extending below the upper edges of the cut-outs 20 and being provided with cover plates 21 for that portion of each member 19 which projects below the edge of the cut-out. Between each channel 19 at the lower end of the skirts 18 is welded or otherwise fixed a plate 21a to reinforce the lower end of the panels 18 and to prevent leakage of earth through the cut-outs 20. The lower portion of each of the cover plates 21 is apertured for the reception of a bearing 22 in which is rotatably'journaled a shaft 23, to the outer end of which is keyed a rotary, toothed disc 24. Each of the discs 24 is located substantially in the plane of its associated plate l8, and it is preferred that the plates 18 be so arranged that the skirt tapers upwardly slightly, as is shown in Figures 1 and 3, for a purpose later to be explained.

Each of the shafts 23 on which the discs 24 are mounted has keyed to its other end a sprocket wheel 25 around which is trained a sprocket chain 26. The chains 26 also are trained around sprocket wheels 27 (Figure 5) mounted on shafts 28 at the upper ends of the housing members 19 so that rotation of the wheels 27 will cause corresponding rotation of the sprocket wheels 25 and the toothed discs 24.

Power driving means D and drive transmission mechanism T is provided for driving all of the augers and the toothed side cutters simultaneously. In the disclosed embodiment of the invention the power driving means D comprises a prime mover such as an internal combustion engine 29 supported above the frame platform 1a by means of mounting bars 30 (see Figures 1 and 10), but other kinds of prime movers may be used and may be supported elsewhere with respect to the digging machine. The motor drive shaft 31 has a multiple groove pulley 32 keyed thereto and a number of V or other suitable belts 33 are trained around the pulley 32 and around a relatively larger multiple groove pulley 34 which is keyed to a shaft 35 journalled in spaced bearings 36 and, 37 (Figure 6) supported on the platform 1a. The shaft 35 is enlarged intermediate the bearings 36, 37 and a portion of the enlarged portion of the shaft is splined as is shown at 38 in Figures 6-8. Mounted on the splined portion of the shaft 35 for rotation therewith is a coupling or clutch member 39 having an inner gear ring 40 adapted to mesh with a spur gear 41 and an outer gear ring 42 adapted to mesh with another gear 43. An operatinglever 44 is provided for effecting sliding movements of the clutch member 39 along the spline shaft 38, the lever 44 being suitably mounted in bearings 4546 (Figure 1) fixed to the frame 1 and having a part 47 extending into an annular groove 48 formed in the clutch member 39. To facilitate operation of the operating lever 44, the latter is provided with a handle 49.

The gear 41 with which the clutch gear 40 is adapted to mesh is the same size as the gear 40 and is mounted fast with a sleeve 50 which is loosely, i.e., rotatably mounted on the shaft 35. Mounted .fast on the sleeve 50 is a first pair of sprocket wheels 51 around which is trained a pair of sprocket chains 52, the chains 52 also passing around a pair of sprocket wheels 53 mounted fast on a jack shaft 54 which is rotatably journaled in bearings 55, 56 suspended from the frame 1. The function and operation of the wheels 51, 53 and the chains 52 will be described subsequently.

Fast on the sleeve 50 is another pair of sprocket wheels 57 around which a pair of chains 58 aretrained, the chains 58 extending downwardly from the wheels 57 as is best shown in Figures 1 and S. The chains 58 are trained about a pair of sprocket wheels 59 mounted fast on a counter shaft 6%, the latter being rotatably journalled in bearings 61, 62 supported on posts 610, 62a mounted on the platform do. At one end of the shaft is keyed a bevel gear 63 which meshes with another, but larger, bevel gear 64 fixed on a vertical shaft 65 which is journalled in a bearing carried by a flange 66 extending outwardly from the post 62a. Intermediate the flange 66 and the bevel gear 64, and fast on the shaft 65, is a sprocket wheel 67 around which is trained a chain 68, the latter also being trained around a relatively large sprocket wheel 6% which is keyed to the shaft 11 of the main or central auger 12.

Referring particularly to Figures 5 and. 9, the main auger shaft 11 is equipped with a second sprocket wheel which revolves with the shaft 11 and is located below the wheel 69 and spaced therefrom by a collar 71. Around the sprocket wheel 70 is trained a chain 72 which also passes over an idler 73 mounted on a post 73a and around a sprocket 74 fixed at the upper end of one of the corner auger shafts 4. This auger shaft 4 has keyed to it a second sprocket wheel 75 below the wheel '74, and each of the other corner auger shafts 4 is provided with a similar sprocket wheel 75. A chain 76 passes around each of the sprockets 75 and the arrangement is such that rotation of the main anger 12 causes all of the corner angers to rotate in unison and at the same speed. The speed of rotation of the corner angers, however, preferably is not the same as the speed of rotation of the main auger. In the disclosed embodiment of the inven tion, the relative sizes of the sprocket wheel units 67 and 69, and 70, 74 and 75 are such that the corner angers S rotate at a speed about twice as fast as the speed of rotation of the main auger 12 for a given power setting of the engine 29.

Referring now particularly to Figures 5 and 10, the end of the shaft 60 remote from the bevel gear 63 has fixed thereto a sprocket wheel 77 which drives, through the intermediary of a chain '78, a sprocket wheel 79 which is keyed to a horizontal shaft 86 supported intermediate its ends on the platform 1a by means of a bearing support 81, the ends 28' of the shaft 8!) corresponding to the parts 28 previously described. Each end 28 of the shaft 36 extends through bearings 82 carried by opposing housing members 19 and has fixed thereto the sprocket wheel 27 which previously has been referred to. Adjacent to one end of the shaft 34 is fixed a sprocket 33 around which a chain 84 is trained. The chain 84 also passes around a sprocket wheel 85 which is keyed to the shaft 28 supported in another housing member 19. A similar arrangement of sprocket wheels 83 and 85 and a connecting chain 84 is included adjacent to the other end of the shaft 80.

On the shaft 86 between its central support 81 and one of the sprockets 83 is keyed a bevel gear 86 which meshes with a pair of opposed bevel gears 87 carried by aligned shafts 28. These shafts are suitably journalcd in bearings 28a and are connected to sprockets 27 mounted in the housing members 19 in the manner previously described. Each of the just referred to shafts 23 carries a sprocket wheel 88 which drives another sprocket wheel 59 through a chain 93, the wheels 89 being mounted on the shafts 28 of the remaining pair of housing members 1%. All of the sprockets 83, $5, 83, and 39 are the same size so that all of the shafts 28 are driven at the same speed. Moreover, the size of the sprockets 83, 85, 88, and 39 is the same as the size of the sprocket wheels 25 and 27 mounted within the housing members 19. As a result, all of the rotary toothed cutters rotate at a uniform speed.

In the operation of the parts described thus far, the digging apparatus is placed in position by suitable means such as a crane (not shown) and the power engine 29 started and set to the desired speed of operation. The clutch member 39 is then moved from its neutral position intermediate the gear 43 and the gear 41 towards the right, as viewed in Figures 6, 7, and 8, soas to engage the gears 49 and 41 and set in operation the drive transmission means T to drive the augers and side cutters in earth boring directions. The engagement of these gears will cause rotation of the sleeve 50 and, consequently, rotation of the sprocket wheels 51 and 58. Rotation of the wheels 51 will cause rotation of the shaft 54 and the gear 43, but since the latter is unengaged, it will rotate idly. Rotation of the sprocket wheels 58, however, will cause rotation of the shaft 60 and, consequently, rotation of the main and corner augers 12 and 8, respectively, and rotation of the side cutters 24 through their respective drive transmitting chains, shafts, and sprockets. The direction of drive of the motor 29 will be so selected that the driving of the augers through the sprockets 58 is in a direction to cause the augers to bore into the earth.

As the driving of the augers and side cutters is begun, the latter will cut into any turf that may be present and the screw threaded ends of the augers will begin boring pilot holes for the flights of the augers. Dug or loose earth will be lifted by the auger flights and the machine will settle into the hole being dug under its own weight. In this connection, it is preferable that the plates 18 be disposed at a slight angle to the vertical so as to taper upwardly with the lowermost edges of the cutters extending slightly beyond a vertical plane extending from the edge of the platform 1a. The purpose of the angular disposition of the plates 18 is to assure the cutting of side walls for the hole of suflicient width to enable the machine to lower itself into the hole being dug without having its progress impeded by friction between the sides of the machine and the sides of the hole. The angular positioning of the plates will not prevent the cutting of substantially straight sides for the hole.

When the machine has settled into the hole being dug a distance about half the radius of the side cutters, the lower edges of the auger flights will be in a position to engage the earths surface. To facilitate boring operations, the leading edges of the central augers flights may be provided with removable or fixed teeth, as is shown at 91 in Figures 2 and 4. At about this same time, the lower edges of the housing members 19 also will be in position to engage the ground. As is shown in Figure 3, it is preferred that the lower ends of the housing members 19 be beveled or pointed as at 91' to facilitate their entry into the ground and also in order that they may push or turn earth inwardly of the machine sides into the path of the main auger.

The arrangement of the augers is best shown in Figure 2. The augers are arranged quincuncially, the main auger 12 being much greater in diameter than the corner augers 8. The diameter of the main auger is such that it is substantially tangential to each of the side walls 18 and to each of the corner augers 8. The diameter of each corner auger is such that it is substantially tangential to two adjacent walls 18. It is not possible for the diameters of the augers to overlap or be exactly tangential to each other or to the side walls because of the interference which would then be present. It is important, however, that as much of the space within the enclosure defined by the side walls 18 be occupied by the augers as is possible in order to prevent the formation of ridges or uncut portions of earth which would offer resistance to the settling of the machine into the hole being dug. To prevent the formation of such ridges between the main auger and the corner augers, each of the flights of the main auger preferably is equipped with the preferably removable, downwardly and radially outwardly extending rake tooth 16 which will sweep under the lower edges of the flights of the corner augers and loosen the earth between the corner and central augers. The teeth 16 also will loosen the earth beneath the housing members 19, but will not interfere with the side cutters 24 or the plates 21a since the teeths outer ends will be angled below the axes of rotation of the cutters 24 and will be free to pass 6 under the plates 21a and past the cutters in the spaces between the latter.

As has been pointed out previously, the flights of the corner augers preferably are at a different pitch than the flights of the main auger, and the corner augers preferably are driven at a faster rate of speed than the central auger. The result of this pitch and speed differential is that some of the loose earth which otherwise would be carried upwardly along the flights 5 of the corner augers will be subjected to centrifugal force and will be spun off the flights 5 onto the flights 13 of the main auger. The preferred speed of rotation of the main anger is such that the loose earth tends to remain on the flights and be carried upwardly.

The driving of the augers in the boring direction continues until such time asthe flights 5 and 13 contain as much loose earth as they can hold. The machine operator may ascertain when this condition has been reached by viewing the augers through openings 92 formed in the side walls 18. At this time the clutch member 39 can be shifted to its neutral position, whereupon rotation of the augers will cease, and the crane or the like operated to withdraw the machine from the hole it has dug. The loose earth will remain on the flights so as to leave a hole which has substantially straight walls and a substantially flat bottom.

The machine can be raised by the crane over a truck or other place where the contained earth is to be unloaded from the machine and the clutch member 39 shifted so that the gear 42 meshes with the gear 43 on the jack shaft 54 as is shown in Figure 8. This will cause the shaft 54 to be driven in a direction opposite to the direction of rotation of the shaft 35, the sleeve 50 being driven in the direction of rotation of the shaft 54 by means of-the sprockets 51 and 53 and the chains 52. It will be appreciated that this direction of drive of the sleeve 50 is opposite to the direction it is driven by engagement of the gears 40 and 41. Thus, the augers will be driven in the direction opposite to the earth boring direction. Due to the larger diameter of the gear 42 relative to the gear 43, the sleeve 50 and the augers will be driven at a much faster rate of speed in the reverse direction than they are in the boring direction at the same power setting of the engine 29. The faster rotation of the augers in the reverse direction will spin the dug earth off the auger flights very rapidly and will even enable sticky substances such as clay to be removed from the augers automatically.

After the machine has been emptied of loose or dug earth, it may be repositioned in the hole to dig a deeper hole, or it may be positioned alongside the first hole to dig a longer trench or grave-like hole.

The disclosed embodiment of the invention is representative of a preferred form of the invention and is intended to be illustrative rather than definitive of the invention. The invention is defined in the claims.

I claim:

1. Earth digging apparatus comprising aframe; a plurality of augers arranged in quincuncial form; means supporting said augers in depending relation from said frame and for rotation relative to said frame; a plurality of panels secured to said frame and depending therefrom to form a single, four-sided enclosure for all of said augers; driving means; and transmission means interconnecting said driving means and said augers for driving the latter in boring direction, the arrangement and sizes of said augers being such that the central auger is substantially tangential to each of said panels and to each of the other augers, and each of the other augers is substantially tangential to two of said panels, whereby driving of said augers will dig a quadrangular hole substantially the size and shape of said enclosure, said central auger clearing earth between each of the other augers.

2. Earth digging apparatus comprising a frame; a plurality of augers arranged in quincuncial form; means supporting said angers in depending relation from said frame and for rotation relative to said frame; a plurality. of panels. secured. to said frame and. depending therefrom to form a single, four-sided: enclosure for all; of said angers, toothed discs. rotatably carried at eachside of said frame and located at the lower edge off said en'- closure in substantially the plane of the latter; driving means; transmission means interconectingsaid driving means and said angers. and said toothed'discsfor driving the angers in boring direction and for rotating the discs, the arrangement and sizes of said angers being such that the central. auger is substantially tangential to each of said panels and to each of the other angers, and each of the other angers is substantially tangential'to two of said panels, whereby driving of said angers will dig a quadrangular hole substantially the size and shape of said enclosure, said central auger clearing earth between each of the other angers.

3. Earth digging apparatus comprising a frame; a main auger and a plurality of other angers arranged in quincnncial form; means supporting each of said angers in depending relation from said frame and for rotation relative to said frame; a plurality of panels secured to said frame and depending therefrom to form a four-sided skirt enclosing said angers; driving means; and transmission means interconnecting said driving means and each of said angers for driving the latter in boring direction at such speed that loose earth will remain on the flights of said main auger, said transmission means including means for reversing the direction of drive of said angers and for driving the main auger at such speed in the reverse direction that loose earth on the flights of the main auger is spun oif, the arrangement and sizes of said angers being such that the main auger is substantially tangential to each of said panels and toeach of the other angers, and each of the other angers is substantially tangential to two of said panels whereby driving of said angers will dig a quadrangular hole substantially the size and shape of said skirt, said main auger clearing earth between each of the other angers.

4. Earth digging apparatus comprising a frame; a main auger and a plurality of other'augers arranged in quincnncial form; means supporting each of said angers in depending relation from said frame and for rotation relative to said frame; a plurality of panels secured to said frame and depending therefrom to form a four-sided skirt enclosing said angers, driving means; transmission means interconnecting said driving means and said angers for driving the latter in boring direction at. such speed that loose earth will remain on the flights of said main auger, said transmission means including means for reversing the direction of drive of said angers and for driving the main auger at such speed in the reverse direction that earth on the flights of the main auger is spun ofi; and toothed discs rotatably carried by said frame and located at the lower edge of said skirt in substantially the plane of the latter, said transmission means interconnecting said driving means and said toothed discs for rotating the discs simultaneously with the driving of said angers.

'5. Earth digging apparatus comprising a frame; a pinrality of panels depending from said frame and arranged to form a quadrilateral enclosure; a plurality of angers within said enclosure arranged in quincnncial form with one anger at each corner of said enclosure; means supporting said angers on said frame for rotation with respect to the latter,- the central auger being of larger diameter than the corner augers'and being substantially tangential to each of said'panels and to each of said corner angers; driving means; and transmission means interconnecting said driving means and saidangers for driving the latter in boring direction whereby said augers' will diga quadrangular hole substantially the size 'of said enclosure,- the central auger clearing earthbetween' each of the corner angers, said panels constituting the sole enclosure for said'angers.

6. Theconstruction set forth in claim 5 including rotatable toothed discs at each side of said' enclosure; and means mounting said toothed discs substantially in the plane of their associated panels and at the lower portion thereof, said transmission means also interconnecting said toothed discs to said driving means for driving said discs conjointly with said angers.

7. The construction set forth in claim 6 in which the mounting means for each of said toothed discs includes a housing member having its lowered portion tapered to force earth inwardly of" said enclosure into the pathof said'augers.

8. The construction set forth in claim 6 inwhich the lower ends of said angers terminate in reduced shaft portions depending below the flights of said angers, and in which said central anger includes a projection carried at the lower end of its flight arranged to extend radially outwardly thereof and below the lowermost flights of the corner angers and below the axis of rotation of each of said toothed discs so as to loosen earth in the vicinity of said tootheddiscs and the corner angers.

9. The construction set forth in claim 5 in which the lower ends of said angers terminate in reduced shaft portions depending below the flights of said angers, and in which said central anger includes a projection carried. at the lower end of'its flight arranged to extend radially outwardly thereof and below the lowermost flights of said corner angers to loosen earth in the path of the corner angers.

10. The construction set forth in claim 5 in which each of said angers includes at least one helical flight, the flights of the corner angers being at a different pitch than the flight of the central anger.

11'. The construction set forth in claim 5 in which said transmission means includes means for driving said corner angers at a rate of speed different from the rate of speed of said central auger.

l2.The construction set forth in claim 5 in which each of said angers includes at least one helical flight, the flights of the corner angers being at a different pitch than the flight of the central anger, and in which said transmission means includes means for driving said corner angers at a rate of speed different from the rate of speed of said central auger.

13. The construction set forth in claim 12' in which the flights of the corner angers are at a steeper pitch than the flight of the central auger.

14. The construction set forth in claim 12 in which the corner angers are driven at a faster rate of speed than the central anger.

15'. The construction set forth in claim 12 in which the flights of the corner angers are at a steeper pitch than the flight of the central auger, and in which the transmission means causes the corner angers to be driven at a faster rate of speed than the central anger.

16. The combination with a plurality of earth boring angers mounted quincuncially in a supporting frame, power means for driving said angers, and transmission means interconnecting said power means and said angers for driving said angers at a selected power setting ofs'aid power means in the boring direction, of means for re.- versing the direction of drive of said angers, said reversing means including changeof speed gearing operable to drive said angers at a faster speed in the reverse direction than in the boring direction at the same power setting.

l7. Earth digging apparatus comprising a frame; a

plurality ofangers arranged in quincuncial form; means supporting each of said' angers in depending relation from said frame and for rotation relative to said frame; driving means; andtransmission means interconnecting said driving means andisaid angers for driving the latter simultaneously inboring direction, said angers being so arrangedthatthe'central anger is substantially tangential 9 to each of the others and the other angers are uniformly spaced about said central anger in such manner that an imaginary line tangential to and enclosing each of said other angers defines a substantially square area, said central anger also protruding between each adjacent pair of 5 said other angers so as to be substantially tangential to said imaginary line between each adjacent pair of said other angers, none of said angers being individually enclosed.

References Cited in the file of this patent UNITED STATES PATENTS 

